Dual feed system for electrocoating bath

ABSTRACT

AN AQUEOUS EMULSION ELECTROCOATING BATH IS MAINTAINED BY SEPARATELY SUPPLYING: (1) AN OIL-IN-WATER EMULSION HAVING AN EMULSIFIED PHASE COMPRISING WATER INSOLUBLE ORGAIC SOLVENT HAVING DISSOLVED THEREIN AN AT LEAST PARTIALLY ESTERFIED RESINOUS POLYOL AND A CONTINUOUS PHASE COMPRISING WATER AND RESINOUS POLYCARBOXYLIC ACID EMULSIFYING AGENT IN PARTICALLY NEUTRALIZED BASE-DEFICIENT CONDITION; AND (2) A PIGMENTED, BASE-SATIFIED, WATER-BERAING AND WATER REDUCIBLE SOLUTION COMPRISING RESINOUS EMULSIFYING AGENT DISSLOVED IN WATER MISCIBLE ORGANIC SOLVENT.

3,723,275 DUAL FEED SYSTEllgiOR ELECTROCOATING TH William Bonfich, Pal-ma, Ohio, and James C. Holfman, Jamesburg, NJ., assignors to Mobil Oil Corporation No Drawing. Filed Mar. 15, 1971, Ser. No. 124,604 Int. Cl. B01k 5/02 US. Cl. 204-181 6 Claims ABSTRACT OF THE DISCLOSURE An aqueous emulsion electrocoating bath is maintained by separately supplying: (1) an oil-in-water emulsion having an emulsified phase comprising water insoluble organic solvent having disssolved therein an at least partially esterified resinous polyol and a continuous phase comprising water and resinous polycarboxylic acid emulsifying agent in partially neutralized base-deficient condition; and (2) a pigmented, base-satisfied, water-bearing and water reducible solution comprising resinous emulsifying agent dissolved in water miscible organic solvent.

The present invention relates to a dual feed system for electrocoating using an emulsion electrocoating bath, and is an improvement for certain purposes over the feed system described in U.S. Pat. 3,335,103. More particularly, greater uniformity of deposition and enhanced throwing power are obtained, and the physical burden of the electrocoater is eased.

In said patent, the feed to the electrocoating bath consists of two separate portions; one being a highly pigmented, water-containing, base-satisfied feed and the other being a base-deficient, water-free feed. The use of two feeds enables continuous operation despite removal of materials from the emulsion system by electrophoretic deposition of coating at the anode of a unidirectional electrical system.

As a peculiarity of operation in accordance with the teachings of Pat. 3,335,103, it has been found that the longer the base deficient, water free feed is stored in the presence of any significant proportion of amine prior to use, the greater is the reduction in operating voltage which results when the replenishment operation is carried out. Of course, at least some amine is required to be present to prevent the amine content of the bath from becoming excessively reduced. Thus, the previous materials had to be used within a few hours after addition of the amine or the electrocoating bath would become impaired depositing films possessing a reduced rupture voltage. This forces the use of lower electrodeposition voltages to insure the deposit of continuous films, and this reduces the throwing power of the system which is quite disadvantageous.

It was previously thought that pre-emulsification of the base deficient, water free feed to form a stable emulsion would require excessive amine, or excessive water, or both. Moreover, it was not seen how any pre-emulsification could alter the electrical instability induced by the presence of the amine, especially since storage prior to use would still be required.

We have now found that when the proportion of water is from 50-100%, based on the weight of total resin and solvent, and when the system is neutralized with base to an extent of from 25% to 45%, based on the acidity of the resins, that stable emulsions can be formed and the electrical characteristics are remarkably stable, there being no noticeable lowering in rupture voltage after 7 weeks of storage. In contrast, one Week storage of the prior water free feed in the presence of base would result in a marked lowering of rupture voltage, e.g., in the nited States Patent 0 3,723,275 Patented Mar. 27, 1973 systems illustrated herein, from about 170 volts to about 120 volts.

In preferred practice, neutralization is from 30-40% and the proportion of water which is used is between 60 and on the basis noted above. Despite the stability of the emulsion from all of the standpoints noted, the amine content is still low enough to keep the amine content of the electrocoating bath under control. Moreover, in many instances, the additional water needed is small enough to avoid any problem of flooding the bath, being approximtaely balanced by the liquid carried out of the tank by the wet electrocoated product.

By pre-emulsifying the prior water free, feed, the only mixing required at the electrocoating facility is a simple blending as might be obtained with a power driven agitator. Proportioning of amine, speedy use of amine-containing material, sophisticated high power emulsifiers or homogenizers and the like are all eliminated.

Both the previously patented and the new feed systems of the present invention have the same composition for the highly pigmented feed portion, though specific pigment selection will depend on desired color and like considerations. Thus, the pigmented feed is a pigmented base satisfied, water bearing and water reducible system in which the Water has dispersed therein a salt of a base with a resinous polycarboxylic acid emulsifying agent having an acid number of at least 40.

The oil soluble phase comprises a resinous polyhydric alcohol at least partially esterified with monobasic carboxylic acid providing easy flowability and compatibility with the resinous emulsifying agent in a deposited film.

The oil soluble phase may desirably include aminoplast resins to facilitate subsequent cure and water immiscible organic solvents to help maintain the two separate phases of the final emulsion.

While several aspects of the invention will be discussed hereinafter, it is desired at this point to illustrate the invention with specific examples.

EXAMPLE 1 Pigmented feed portions: Weight percent Basic lead silico chromate pigment 64.15 Surfactant (water dispersible soya lecithin) 3.21

Dehydrated castor oil/cyclopentadiene modified linseed oil/maleic anhydride resin at 82.5% solids in ethylene glycol monoethyl ether (see Example 2A) 8.64 Ethylene glycol monoethyl ether 1.58 Diethylamine 1.61 Tap water 20.81

Blend the surfactant, 50% of the linseed oil/maleic anhydride resin, 50% of the ethylene glycol monoethyl ether, 21% of the diethylamine and 13% of the tap water in a mixing vessel and stir well. Add another 45% of the diethylamine and another 50% of the tap water to the mixing vessel, stir well and charge the entire amount to a suitably sized pebble mill. Charge the pigment to the pebble mill and after a short run of the mill a check of the viscosity should be made. The viscosity is 84 Krebs units, but it can be permitted to vary in the range of 82-86 Krebs units. If needed, add a small amount of tap water to attain the desired viscosity. Grind until a fineness of 6% minimum is obtained (64-72 hours are normally required). The North Standard fineness scale is used herein.

In a separate mixing vessel blend the balance of the linseed oil/maleic anhydride resin, ethylene glycol monoethyl ether, diethyl amine and tap water. Charge this blend to the mill after the grind is satisfactory, then continue the grind for one hour and discharge through a strainer to obtain the final product ready for use as feedstock.

It will be noted in passing that this example illustrates presently preferred pigmentation, though the somewhat different pigmentation shown in US. Pat. 3,335,103 i also useful.

EXAMPLE 2 The dehydrated castor oil/cyclopentadiene modified linseed oil/maleic anhydride resin of Example 1 is made as follows.

2064 pounds of cyclopentadiene-modified linseed oil are admixed with 2064 pounds of dehydrated castor oil and heated to 450 F. in 2 hours while under a nitrogen blanket. The mixture is held at 450 F. for 1 hour, there being no viscosity increase during this period. The mixture is then cooled to 230 F. over a period of 90 minutes and 584 pounds of maleic anhydride are added whereupon the temperature is raised to the range of 380 F. in 1 hour. Cooling is used as needed to control the exotherm and the temperature is maintained at 380-420 F. for from 1-3 hours until the final Gardner-Holt viscosity of U is reached, the viscosity being measured at 77 F. in a 70% solution in mineral spirits. The product is cooled to 220 F. in 2% hours. The acid number (alcoholic KOH) is about 71.

The mixture is then placed under total reflux and 82 pounds of water are added to the bottom of the kettle over a period of 45 minutes. The heat is increased gradually over 1% hours to a temperature of 280 E. which is held for 1 hour until the acid value (alcoholic KOH) is in the range of 100-104 whereas the acid value measured in aqueous KOH is less than units higher. Any unreacted water is then removed by vacuum of sparging. The Gardner-Holt viscosity at 70% non-volatile in mineral spirits is Z but the viscosity may vary from Z to Z The resin so-provided is then reduced by dropping the same into a blend of 329 pounds of ethylene glycol monoethyl ether and 849 pounds of 4-methoxy, 4-methyl pentanone-2 and filtered to provide a yield of 700 gallons at 80.0% non-volatile solids, with the weight per gallon being 8.36 pounds.

EXAMPLE 2A Example 2 is repeated, but with a modification in the reducing procedure. In this example, the resin is dropped into 1000 pounds of ethylene glycol monoethyl ether to yield 680 gallons at 82.5% non-volatile solids, with a weight per gallon of 8.36 pounds.

EXAMPLE 3 The composition of the new feed which supplies the oil phase resin in emulsion form and its method of manufacture are set forth below.

BLACK SEMI-PASTE Ingredient: Weight percent Carbon black pigment in bead form 3.06 Resin of Example 2A at 82.5% solids 0.35 Oil soluble resin at 72.5% solids (see Example 5) 87.36 n-Butyl alcohol 5.15 Aromatic hydrocarbon solvent (Solvesso 150) 4.02 Diethyl amine 0.06

Premix the Example 2A resin, the amine and 82% of the n-butyl alcohol and transfer the mixture to a suitably sized pebble mill. Add the pigment to the mill and roll for 1 /22 hours. In a separate container blend the balance of the n-butyl alcohol, 53% of the aromatic hydrocarbon solvent and 8% of the oil soluble resin, and add to the mill. The viscosity of the mill charge is Krebs units, but it may vary in the range of 85-95 Krebs units. Grind to a fineness of 7 /2 minimum-normally requires 72 hours. When the fineness has been attained, add an additional 7.5% of the oil soluble resin and grind an additional 16 hours. The fineness should still be 7% minimum (North Standard scale). In a separate container, blend the balance of the aromatic hydrocarbon and an additional 18% of the oil soluble resin. This blend is added to the mill and the mill rolled 1 additional hour, then discharged into a mixing vessel. While keeping the paste under agitation, the balance of the oil soluble resin is added. After all the resin has been added, mixing is continued for an additional 30 minutes. The final product has the following physical constants;

Weight per gallon, pounds 3.23 Viscosity, Krebs units 7- /2 Fineness (North Standard), minimum 7% Non-volatile content, percent 65-68 EXAMPLE 4 Oil phase feedstock emulsion Ingredient: Weight percent Black semi-paste of Example 3 25.78

Oil soluble resin at 72.5% solids of Examample 5 6.91 Resin of Example 2 (80.0% solids) 25.43 Diethyl amine 1.35

Aromatic hydrocarbon solvent (Solvesso 0.54 Ethylene glycol monoethyl ether 0.56 Tap water 39.43

To a suitable mixing vessel equipped to impart high shear or slow agitation are required, charge the black semi-paste and the oil soluble resin and blend under slow speed. In a separate container blend the Example 2 resin, ethylene glycol monoethyl ether and aromatic hydrocarbon. Add this blend to the semi-paste mixture and under slow speed mix for 5 minutes. While continuing slow agitation, add the diethyl amine slowly and continue mixing slowly for an additional 5 minutes. Convert to high shear agitation and add the tap water in four equal portions to emulsify the system. As the last portion of tap water is being added, it may be necessary to decrease the shear to prevent excessive foaming, and because the system will have inverted from a water-in-oil emulsion to an oil-in-water emulsion.

EXAMPLE 5 Oil soluble resin at 72.5 solids The oil soluble resin at 72.5% solids is prepared according to the teachings of Example XIII of US. Pat. 3,335,103 except for the actual weights of ingredients used.

1398 pounds of tall oil fatty acid (containing 4% of rosin acids) and 467 pounds of oiticica oil are mixed and heated to 250 F. in 1% hours using an inert gas sparge. 621 pounds of rosin are mixed with 776 pounds of a heat reactive, phenol-formaldehyde resin and 2198 pounds of styreneallyl alcohol copolymer A (see US. Pat. 3,335,- 103, column 8, lines 1-18). This mixture is then added to the tall oil fatty acid-oiticica oil mixture over a 40 minute period which drops the temperature to about 200 F. Heat is then applied to raise the temperature to 400 F. in 1% hours and held at this temperature for about 1 hour to obtain a viscosity of Z-5 and an acid number of 36-38. The oil soluble resin so produced is then thinned with 273 gallons of aromatic hydrocarbon solvent (Solvesso 150) to provide 892 gallons of organic solvent solution having the following specifications:

Non-volatiles, percent 72.5 Gardner-Holt viscosity Z- Acid number 36-38 Weight per gallon, pounds 8.26

The initial electrocoating composition, for which Examples 1 and 4 constitute the improved replenishment feed system, is detailed below.

Highly pigmented feed stock of Example 1 8.83 Black semi-paste of Example 3 26.64

To a suitable mixing vessel equipped to impart high shear or slow agitation as required, charge the Example 2 resin and the ethylene glycol monoethyl ether. Begin mixing at a moderate rate and slowly add the diethyl amine. When all of the diethyl amine has been added, continue mixing for an additional minutes. At this time slowly add 31% of the tap water and allow the batch to mix for an additional 10 minutes. Then add the Example 1 highly pigmented feed stock and continue moderate agitation for 10 minutes to insure uniform blending of all materials. Convert to high shear agitation and slowly add the Example 3 black semi-paste. It is imperative that the black semi-paste be added into the vortex created by the high shear agitation to insure the best possible emulsification of the oil phase components. Continue high shear agitation for minutes and then slowly add the remaining tap water in three equal portions. When about half of this water has been added, a sharp drop in the viscosity of the batch may occur indicating the inversion of the system from a water-in-oil emulsion to an oil-in-water emulsion. When this has occurred, the high shear agitation must be gradually reduced to prevent excessive foaming in the batch.

When all components have been added, the batch is mixed for an additional 15 minutes under slow agitation. Specifications on the completed material are shown below:

Non'volatiles, percent 40.5 Viscosity-#4 Ford Cup, seconds 25-40 Lead silico chromate pigment( based on total solids of paint), percent 14 Carbon black pigment (based on total solids of paint), percent 2 p 8.4-8.6 Fineness (North Standard) 7-7 /2 Conductivity (micro mhos) 2000-3000 Weight per gallon, pounds 8.6

Prepare the electrocoating bath by mixing one volume of the paint described above with three volumes of water to obtain a coating bath containing 1011% solids material. Agitate the bath (slowly) for four hours, then adjust the temperature to 70 F. and check the pH. If the pH is below 8.9, adjust the batch with a small amount of diethyl amine so that the final bath pH falls into the range of 8.9-9.1. The bath is now in the proper condition for electrodeposition. Films of 0.60.8 mil in thickness and jet black in color should be obtained at a minimum of 170 direct current volts.

Under normal operating conditions, it is desirable to maintain a weight concentration of 14% of basic lead silico chromate pigment (based on the total solids of the bath) in the coating tank. To supply the pigment at this same concentration requires a feed ratio of 1 gallon of the feed of Example 1 containing the lead pigment to 17.5 gallons of the emulsion feed component of Example 4.

The following example illustrates in greater detail a typical procedure for maintaining an electrocoat bath prepared from the initial fill paint formulation shown in Example 6.

EXAMPLE 7 Consider an electrocoat tank with a capacity of 12,000 gallons. To this tank is added 3000 gallons of the initial fill electrocoat formulation shown above and 9000 gallons of water to yield 12,000 gallons of electrocoat bath. A sample of the bath is analyzed and found to contain 10% non-volatile solids and 14% non-combustible pigment (based on total weight of solids) or ash. The weight per gallon of the bath is determined to be 8.33 pounds. This information leads to the following table of data for the composition of tank at start up.

TABLE I Gallons 12,000 Total weight of bath (pounds) 100,000 Total weight of solids (pounds) 10,000 Total ash (pounds) 1,400

Assume that the items being coated are of such a size and surface area that they are totally immersed in the electrocoat bath for 2 minutes coating time, and that the tank is operating at 200 DC volts to deposit a film averaging 0.75 mil in thickness on all surfaces of the items in question. Further assume that the weight of coating deposited on each item averages 5.0 pounds and that 20 such items are coated per hour for a total of 320 items coated in a two shift, 16 hour working day. To simplify this example, let us also assume that the deposited film is non-volatile solids, and that the composition of the deposited film solids is identical to that of the bath (i.e., the percent pigments in the film equals the percent pigment in the bath). Also, for the sake of simplicity, assume that any bath clinging to the coated items as they emerge from the coating bath is completely drained ofl each item and back into the tank so no volatiles are removed from the tank by any other process and that solids depletion occurs exclusively through electrodeposition.

Given these conditions, We can perform a set of simple calculations to determine how much of each of our feed materials should be added to our hypothetical tank to maintain a material balance of 10% non-volatile solids and 14% ash (based on total solids). The total weight of solids removed from the tank in one day is 320 items coated per day multiplied by 5.0 pounds of solids per item, which equals 1600 pounds of solids removed per day. Of this 1600 pounds, we are assuming that 14% is the pigment basic lead silico chromate:

.14 1600=224 pounds ash Since the weight per gallon of the solids removed is very nearly 10.0 pounds, the volume removed from the tank is:

1600 pounds -10 pounds/gallon gallons Referring back to Table I, we can now establish the condition of the tank after one day of operation if no feed were added.

The percent solids have dropped to 8.5%, and the percent ash has, of course, remained at 14%. As stated previously, it is desired to maintain the solids content at the desired level while maintaining 14% basic lead silico chromate pigment. Based on these solids, a combination of 1 gallon of Example 1 feed for every 17.5 gallons of Example 4 feed should be used. The composition of this combination is detailed below:

TABLE III Total Total weight weight of solids Total Galof feed in feed ash lons (lbs.) (lbs.) (pounds) Example 1 iced 1. 15. 98 11. 90 10. 25 Example 4 feed 17.5 144. 90 61.60 0 Desired teed combination... 18.5 160.88 73.50 10.25

This feed combination has the desired ash level of 14% based on total weight of solids and it has a solids content of 45.8%. To determine how much of the desired feed combinationshould be added to our tank to restore the composition to non-volatile solids while maintaining 14% ash, we must solve the following equation:

Equation 1 Weight of solids in tank+weight of solids in feed Total weight of bath in tank-l-total weight of feed Let X=total weight of feed then .458)G=weight of solids in feed. From Table II:

89,400=total weight of bath in tank 8,400=total weight of solids in tank Substituting these values in Equation 1 and solving for X, we obtain the following:

98,400+X =O'1O 8400 +.458X=9840 +0.1X .358X=1440 X =4020 pounds of combined feed Example 1 Feed:

Weight to be added=0.10 4020=402 pounds Volume to be added=402 pounds+15.98#/gal.

: gallons25 gallons Example 4 Feed:

Weight to be added=0.90 4020=3618 pounds Volume to be added=3618 pounds:-8.28 pounds/gal.

e ggallons438 gallons From Equation 1, the weight of solids added with 1 4020 pounds of the desired feed combination is:

.45 8X4020l840 pounds The total volume of the feed to be added is 25 gallons Example 1 feed+438 gallons Example 4 feed for a total 8 of 463 gallons. From Table III, the weight of ash contained is 10.25 pounds ash per gallon multiplied by 25 gallons which equal 256 pounds. Table 'II can now be rewritten to show how the tank is restored to its original condition of 10% non-volatile solids and 14% ash based on solids:

TABLE IV Total Total weight of Total Galweight solids ash Remarks lons pounds (pounds) (pounds) Initial bath 12, 000 100,000 10,000 1, 400 Solids removed in one day of operation 160 1, 600 1,000 224 Composition of tank at end of day one if no feed is added 11, 840 98,400 8,400 1,176 Feed to be added:

Example 1 feed +25 +402 +300 +256 Example 4 feed +438 +3, 618 +1, 542 0 Composition of tank after one day of operation with feeding 12,303 102, 420 10, 242 1,432

Since both of the feed materials are readily dispersible in the 10% solids bath, the equipment required for incorporation of these feeds into the electrocoat tank is simple in design and low in cost. For example, a feed premix tank of 200 gallon capacity mounted next to the main electrocoat tank is so designed that bath from the main tank is pumped into the feed tank at the rate of 15 gallons per minute and returned to the main tank by a suitable gravity return overflow system to maintain a constant bath level in the feed premix tank. The total amounts of each feed required for one day of operation are blended in a feed reservoir of appropriate capacity. The blend of feeds is pumped from the reservoir to the premix tank at a constant rate, e.g., a suitably slow rate to provide balanced replenishment of solids in the main tank. To guarantee uniform transfer of solids from the feed reservoir, through the premix tank, and into the main tank, both the feed reservoir and the feed premix tank are equipped with modest agitation.

While the increase in bath volume shown in Table IV may appear somewhat anomalous, it is logical when one compares the non-volatile content of the combined feed materials (45.8%) with the non-volatile content of the deposited film (100%). The only way this volume increase could be avoided in our ideal tank would be to supply a feed material of the same non-volatile solids as the deposited film. The increase in volume is, in fact, the volume of the volatiles in which the replacement solids are dispersed. In this example, the volume increase has been aggravated by the ideal conditions which were established to simplify the calculations. These ideal conditions ignore all of the very real ways in which volatiles are removed from the bath. One of the most important of these is removal through drag-out. The items emerging from the electrocoat bath are covered with a thin film of bath which can only be removed by subsequent rinsing. Since the rinsate is not normally returned to the electrocoat tank, the bath which has been dragged out by each item will be lost. The drag-out per item coated is often quite significant, especially when the item is of a complex shape.

Another corrective factor is the solids of the deposited film. This figure is more realistically placed in the to range rather than at the ideal level. Since the bath contains a significant amount of organic solvents of varying solubility in water, equilibrium requires that some portion of the available solvents be deposited in the film.

Evaporation is a third factor which may assist in the depletion of volatiles, but its role may vary greatly with the operating temperature of the tank, as well as with the volatility of the solvents in question.

To summarize, let us say that the tendency toward volume increases in any continuous electrocoating process are countered by drag-out, deposition, and evaporation of volatiles. If, in any specific application of the feed system described herein, these factors are rendered insufficient to control the phenomenon of increasing bath volume, then other techniques are available as known inthe art.

The dual feed system described above produces a significant improvement in electrical stability. Thus, the initial fill will typically deposit a film 0.75 mil in thickness at 170 volts, and the system of this invention maintains these electrical characteristics. In contrast, if one. were to proceed as described in U.S. Pat. 3,335,103, and form a concentrated emulsion including the amine component, this concentrate being intended to be reduced with 3 volumes of tap water for addition to the electrocoat bath, then storage of the concentrate for as little as 16 hours prior to dilution will cause the voltage required to deposit a 0.75 mil film to drop from 170 volts down to the range of 110-130 volts. This drop in operating voltage is detrimental since it is accompanied by a considerable loss in throwing power. As a result of this electrical instability, it becomes necessary to have an electrocoat operator add the correct amount of amine to the feed immediately'prior to use which leads to innumerable problems, including the direct handling to amines which are not only offensive in odor, but highly flammable. Moreover, it also requires that the operator precisely control the amount of amine addition which is critical to effective operation of the bath and it is obviously desirable to avoid placing such a burden on the operator.

In contrast, the incorporation of the amine into the Example 4 feed stock-emulsion avoids all of the above problems. The Example 4 feed is both physically and electrically stable for a period of at least two months. No degradation of electrical properties have been observed in the Example 4 feed until weeks after manufacture. During this 10 week period, paints made from the Example 4 feed consistently deposit high quality films of 0.75 mil thickness in the desired range of 170 to 200 direct current volts. 4

Referring more particularly to the aqueous emulsion which is maintained, the emulsion comprises a continuous aqueous phase having dispersed therein a salt of a base with a resinous polycarboxylic acid emulsifying agent. Any resinous material having an acid number of at least 40 and which dissolves in water with the aid of a base can be relied upon for emulsification, though it is preferred to use a heat reaction product of aliphatic alpha, beta-ethylenically unsaturated carboxylic acid with polyester of unsaturated fatty acid and aliphatic polyhydric alcohol as more fully detailed in said U.S. Pat. 3,335,103.

The selection of the base for salt formation with the carboxyl groups of the emulsifying agent is not of primary significance. Ammonia, various amines and monovalent metals such as sodium or potassium are all well known and useful as the base.

The oil soluble phase which is dispersed in the aqueous phase comprises a resinous polyol at least partially esterified with monobasic carboxylic acid, the ester groups providing easy fiowability and compatibility with the resinous emulsifying agent in a deposited film. The resinous polyols and the partial esters are more fully described in said Pat. 3,335,103.

The weight ratio of the two different resins in the final bath may vary widely from 10/90 to 90/10.

IAS previously explained, two feeds are used to maintain the emulsion as the solids content thereof is depleted by electrophoretic deposition. The pigmented base-satisfied, water-bearing and water reducible solution which comprises the resinous emulsifying agent dissolved in water miscible organic solvent may be the same as described in said Pat. 3,335,103, but we now prefer to use the materials of Examples 1 and 4 herein since our present customers prefer a black coloration. However, the oil phase resin is differently supplied.

More particularly, the oil phase resin is supplied in the form of an oil-in-water emulsion. In this emulsion, the oil soluble emulsified phase comprises water insoluble organic solvent having dissolved therein at least partially esterified resinous polyol. The same or different resinous polyols and monocarboxylic acids used to supply the emulsifying agent may be used, but no significant acid content may be present which might interfere with the maintenance of a distinct dispersed phase. The water immiscible organic solvents illustrate by aromatic hydrocarbon solvents like toluene and xylene, and long chain alcohols, such as isooctyl alcohol, help to maintain the separate phases of the emulsion.

The emulsified particles are maintained in stable emulsion by a resinous polycarboxylic acid emulsifying agent in partially neutralized base-deficient condition. It has been found that base can be added to the resinous polycarboxylic acid emulsifying agent in an amount of from 25% to 45% (preferably 30% to 40%) of that required by stoichiometry to effect neutralization thereof, together with a small portion of water, from 50% to 100% (preferably 60% to based on total resin and solvent in the emulsion, to thereby form a stable emulsion (high speed agitation being needed to establish the emulsion). The result is a stable oil-in-water emulsion which can be adder to the emulsion electrocoating bath with simple mixing and the emulsion can be formed uniformly, time after time, to enable film deposition properties to be standardized and maximized including the achievement of superior throwing power.

The invention is defined in the claims which follow.

We claim:

1. A method of supplying the components of an aqueous emulsion from which pigment and resin solids have been electrophoretically deposited and carried away, said emulsion comprising a continuous aqueous phase having dispersed therein a salt of a base with a resinous polycarboxylic acid emulsifying agent having an acid number of at least 40, and an oil soluble phase stably dispersed in said aqueous phase by means of said resinous emulsifying agent, said oil soluble phase comprising resinous polyol at least partially esterified with monobasic carboxylic acid providing easy flowability and compatibility with said resinous emulsfying agent in a deposited film, said resinous emulsifying agent and said resinous polyol ester being present in said emulsion in a weight ratio of from 10/90 to /10 comprising: supplying to said aqueous emulsion (1) an oil-in-water emulsion comprising an oil soluble emulsified phase comprising water insoluble organic solvent having dissolved therein said at least partially esterified resinous polyol and a continuous phase comprising water and said resinous polycarboxylic acid emulsifying agent neutralized to an extent of from 25% to 45%, said emulsion containing water in an amount of from 50% to based on total resin and solvent in the emulsion; and (2.) a pigmented, base-satisfied, waterbearing and water reducible solution comprising said resinous emulsion agent dissolved in water-miscible organic solvent using the emulsion for further electrodeposition.

2. A method as recited in claim 1 in which said resinous polycarboxylic acid emulsifying agent is neutralized to an extent of from 30-40%.

3. A method as recited in claim 2 in which the oil-inwater emulsion of said supply component (1) contains water in an amount of from 60 to 80 based on total resin and solvent in said supply component (11).

4. A method as recited in claim 3 in which said oil-inwater emulsion comprises discrete emulsion particles of partially esterified styrene-allyl alcohol copolymer dissolved in aromatic hydrocarbon solvent, said particles 11 being maintained in emulsion with a maleated oil partially neutralized with an amine.

5. A method as recited in claim 1 in which said water insoluble organic solvent comprises aromatic hydrocarbon solvent.

6. A method as recited in claim 1 in which said resinous polycarboxylic acid emulsifying agent is a heat reaction product of aliphatic alpha,beta-ethy1enically unsaturated 12 carboxylic acid with polyester of unsaturated fatty acid and aliphatic polyhydric alcohol.

References Cited UNITED STATES PATENTS 3,335,103 8/1967 Huggard 204-181 HOWARD S. WILLIAMS, Primary Examiner Um'fisn smss PATENT owes @E'HFEEATE @F @QRREUHQN Patent No. 3,723,275 F Dated M h 27, 1973 Inventor) WILLIAM BONFICH and JAMES C,.HOFFMA1\I it is certified their error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, Line 15, ffdisssolved" should be '--dissolved-. a?

Column 3 Line 34, of" should be --or--.

Column LL, Line 4, "the" should be this. Column LL, Line 16, "3023" should be "8,23".

Column LL, Line 17, "7 1/2" should be --11o-12o Krebs Units-. Column LL, Line 39, "are" should be -as-.,

Column 7, Lihe'35',' "89 LL00" should be --98,LLOO--. Column 9, Line 2 4, "an' should be --'--the----.

Column 9, Line 27, i "to" should be -of- Column 10, Line 29, *edder" should be -added. Column 10, Line 62, after "solvent" insert Signed and sealed this 20th day of November 1973.

(SEAL) Attest:

' MQFLETCHERQJRV, RENE D EGTMEYER Attesting Officer Acting Commissioner of Patents 

